Diesel cats are different compounds inside than gasoline cats. The last one we put on a Sterling version of the old Ford L8000 was $1100. The recycle yard paid almost $400 for the scrap one (probably why so many get stolen).
We used to run a semi-syn in Lisa's 800 Intruder, good old Castrol Syntech. Then they changed the formula... it isn't bike safe. If you are buying the so called bike specific from Spectro or Castrol, it's just car oil. I've talked to their reps way too many times to run either in a wet clutch air cooled.
And be leery of Bill, he seems to like cherry Kool-aid colored repackaged snowmobile oil for some odd reason.